This invention relates to an engine intake system and more particularly to an improved high efficiency intake system for engines that improves running throughout the engine speed and load ranges.
It has been found that engine induction efficiency and combustion, particularly at low and medium speeds may be improved by providing an auxiliary intake that communicates with the combustion chamber and which has a relatively small effective area. Such auxiliary intakes have been found to give rise to a high velocity and turbulence in the combustion chamber at the time of ignition that improves flame propagation and engine running. Such devices also improve charging efficiency by minimizing pulsations in the intake system.
Such auxiliary systems are particularly advantageous if disposed in such an arrangement so as to impart a swirl to the charge delivered by the auxiliary system. It is also advantageous to have the auxiliary intake system communicate with the combustion chamber through the main intake passage. Such an arrangement eliminates the necessity for separate intake valves and lessens the complexity of the cylinder head configuration. However, with conventional intake systems, it has been difficult to provide an auxiliary intake that has the desired location and which will be easy to manufacture and not interfere with the configuration of the main intake passage. This is particularly true in multi-cylinder engines in which aligned intake cylinders are employed since the intake passages from one cylinder may interfere with the intake passages and auxiliary intake passages of the next adjacent cylinders.
It is, therefore, a principal object of this invention to provide an improved induction system for an internal combustion engine.
It is another object of the invention to provide an engine induction system wherein both main and auxiliary intake passages may be formed and the auxiliary intake passage located so that a high degree of swirl may be generated.
The amount of swirl generated by the auxiliary intake passage can be increased if the main intake passage is located at an offset relationship to the axis of the associated cylinder. If this is done, the auxiliary intake passage may be positioned at one side of the main intake passage and in close proximity to the periphery of the bore of the associated cylinder. With such an arrangement, however, it is difficult with prior art type of constructions so as to locate both the main and auxiliary intake passages so they do not interfere with each other and so that they do not interfere with the intake passages of the next adjacent cylinder of an in-line engine. Furthermore, the prior art constructions of this type have given rise to considerable problems in connection with the location and formation of the auxiliary intake port and passage by means of a simple machining operation.
It is, therefore, a still further object of this invention to provide an improved intake system for an internal combustion engine wherein at least one of the main intake passages is offset from the cylinder bore axis and the auxiliary intake passage which communicates with the combustion chamber through the main intake passage is offset relative to the main intake passage and in close proximity to the wall of the associated cylinder so as to promote swirling.
In conjunction with the use of auxiliary intake passages as aforedescribed, it has been found advantageous to provide a plenum chamber or volume that supplies the auxiliary intake passage. By employing such a plenum chamber or volume, it has been found that the flow of the intake charge in the intake passage may be stabilized even at low speed and pulsations eliminated or substantially reduced. Where a V type engine is employed, however, it is difficult at times to provide an appropriate location for such a plenum chamber. This is particular true in conjunction with motorcycles where size is of a premium and in conjunction with multiple cylinder engines which employ separate plenum chambers for each chamber.
It is, therefore, a still further object of this invention to provide an improved, compact high efficiency induction system for a V type engine.
In conjunction with V type engines, the cylinders of the cylinder banks are normally staggered slightly from each other. As a result, with prior art type of induction systems, the intake passages are also staggered with respect to each other. Such staggered intake passages give rise to complex induction systems and also can limit the type of carburetion which is employed. That is, if the intake ports of the engine are not aligned with each other, it may be necessary to use a separate carburetor for each intake port.
It is, therefore, a still further object of this invention to provide an improved induction system for a V type engine wherein the intake ports of the respective cylinders are aligned with each other.